In the related art, auto leveling control of automatically adjusting an optical axis position of a vehicle headlight in accordance with an inclined angle of a vehicle and changing an illumination direction of the headlight has been known. In general, during the auto leveling control, the optical axis position of the headlight is adjusted on the basis of a pitch angle of the vehicle deduced from an output value of a vehicle height sensor. Regarding this, Japanese Patent Application Publication No. 2012-106719A discloses a control device of a vehicle lamp device configured to perform the auto leveling control by using an acceleration sensor.
When the acceleration sensor is used, it is possible to make an auto leveling system at lower cost and lighter, as compared to a configuration where the vehicle height sensor is used.
As a result, it is possible to make the vehicle at low cost and light. In the meantime, even when the acceleration sensor is used, there is always a need to further increase precision of the auto leveling control.